Disruption of BMP4 signaling is associated with laryngeal birth defects in a mouse model

Laryngeal birth defects are considered rare, but they can be life-threatening conditions. The BMP4 gene plays an important role in organ development and tissue remodeling throughout life. Here we examined its role in laryngeal development complementing similar efforts for the lung, pharynx, and cranial base. Our goal was to determine how different imaging techniques contribute to a better understanding of the embryonic anatomy of the normal and diseased larynx in small specimens. Contrast-enhanced micro CT images of embryonic larynx tissue from a mouse model with Bmp4 deletion informed by histology and whole-mount immunofluorescence were used to reconstruct the laryngeal cartilaginous framework in three dimensions. Laryngeal defects included laryngeal cleft, laryngeal asymmetry, ankylosis and atresia. Results implicate BMP4 in laryngeal development and show that the 3D reconstruction of laryngeal elements provides a powerful approach to visualize laryngeal defects and thereby overcoming shortcomings of 2D histological sectioning and whole mount immunofluorescence.

Interactions between SOX factors and Wnt/beta-catenin signaling in development and disease

The SOX family of transcription factors have emerged as modulators of canonical Wnt/beta-catenin signaling in diverse development and disease contexts. There are over 20 SOX proteins encoded in the vertebrate genome and recent evidence suggests that many of these can physically interact with beta-catenin and modulate the transcription of Wnt-target genes. The precise mechanisms by which SOX proteins regulate beta-catenin/TCF activity are still being resolved and there is evidence to support a number of models including: protein-protein interactions, the binding of SOX factors to Wnt-target gene promoters, the recruitment of co-repressors or co-activators, modulation of protein stability, and nuclear translocation. In some contexts, Wnt signaling also regulates SOX expression resulting in feedback regulatory loops that fine-tune cellular responses to beta-catenin/TCF activity. In this review, we summarize the examples of Sox-Wnt interactions and examine the underlying mechanisms of this potentially widespread and underappreciated mode of Wnt-regulation.

Sfrp5 coordinates foregut specification and morphogenesis by antagonizing both canonical and noncanonical Wnt11 signaling

Cell identity and tissue morphogenesis are tightly orchestrated during organogenesis, but the mechanisms regulating this are poorly understood. We show that interactions between Wnt11 and the secreted Wnt antagonist secreted frizzled-related protein 5 (Sfrp5) coordinate cell fate and morphogenesis during Xenopus foregut development. sfrp5 is expressed in the surface cells of the foregut epithelium, whereas wnt11 is expressed in the underlying deep endoderm. Depletion of Sfrp5 results in reduced foregut gene expression and hypoplastic liver and ventral pancreatic buds. In addition, the ventral foregut cells lose adhesion and fail to form a polarized epithelium. We show that the cell fate and epithelial defects are due to inappropriate Wnt/beta-catenin and Wnt/PCP signaling, respectively, both mediated by Wnt11. We provide evidence that Sfrp5 locally inhibits Wnt11 to maintain early foregut identity and to allow an epithelium to form over a mass of tissue undergoing Wnt-mediated cell movements. This novel mechanism coordinating canonical and noncanonical Wnt signaling may have broad implications for organogenesis and cancer.

Sox17 and Sox4 differentially regulate beta-catenin/T-cell factor activity and proliferation of colon carcinoma cells

The canonical Wnt pathway is necessary for gut epithelial cell proliferation, and aberrant activation of this pathway causes intestinal neoplasia. We report a novel mechanism by which the Sox family of transcription factors regulate the canonical Wnt signaling pathway. We found that some Sox proteins antagonize while others enhance beta-catenin/T-cell factor (TCF) activity. Sox17, which is expressed in the normal gut epithelium but exhibits reduced expression in intestinal neoplasia, is antagonistic to Wnt signaling. When overexpressed in SW480 colon carcinoma cells, Sox17 represses beta-catenin/TCF activity in a dose-dependent manner and inhibits proliferation. Sox17 and Sox4 are expressed in mutually exclusive domains in normal and neoplastic gut tissues, and gain- and loss-of-function studies demonstrate that Sox4 enhances beta-catenin/TCF activity and the proliferation of SW480 cells. In addition to binding beta-catenin, both Sox17 and Sox4 physically interact with TCF/lymphoid enhancer factor (LEF) family members via their respective high-mobility-group box domains. Results from gain- and loss-of-function experiments suggest that the interaction of Sox proteins with beta-catenin and TCF/LEF proteins regulates the stability of beta-catenin and TCF/LEF. In particular, Sox17 promotes the degradation of both beta-catenin and TCF proteins via a noncanonical, glycogen synthase kinase 3beta-independent mechanism that can be blocked by proteasome inhibitors. In contrast, Sox4 may function to stabilize beta-catenin protein. These findings indicate that Sox proteins can act as both antagonists and agonists of beta-catenin/TCF activity, and this mechanism may regulate Wnt signaling responses in many developmental and disease contexts.

Global analysis of the transcriptional network controlling Xenopus endoderm formation

A conserved molecular pathway has emerged controlling endoderm formation in Xenopus zebrafish and mice. Key genes in this pathway include Nodal ligands and transcription factors of the Mix-like paired homeodomain class, Gata4-6 zinc-finger factors and Sox17 HMG domain proteins. Although a linear epistatic pathway has been proposed, the precise hierarchical relationships between these factors and their downstream targets are largely unresolved. Here, we have used a combination of microarray analysis and loss-of-function experiments to examine the global regulatory network controlling Xenopus endoderm formation. We identified over 300 transcripts enriched in the gastrula endoderm, including most of the known endoderm regulators and over a hundred uncharacterized genes. Surprisingly only 10% of the endoderm transcriptome is regulated as predicted by the current linear model. We find that Nodal genes, Mixer and Sox17 have both shared and distinct sets of downstream targets, and that a number of unexpected autoregulatory loops exist between Sox17 and Gata4-6, between Sox17 and Bix1/Bix2/Bix4, and between Sox17 and Xnr4. Furthermore, we find that Mixer does not function primarily via Sox17 as previously proposed. These data provides new insight into the complexity of endoderm formation and will serve as valuable resource for establishing a complete endoderm gene regulatory network.

Peroxynitrites and impaired modulation of nitric oxide concentrations in embryos from diabetic rats during early organogenesis

Maternal diabetes significantly increases the risk of congenital malformation, a syndrome known as diabetic embryopathy. Nitric oxide (NO), implicated in embryogenesis, has been found elevated in embryos from diabetic rats during organogenesis. The developmental signaling molecules endothelin-1 (ET-1) and 15-deoxy delta(12,14)prostaglandin J2 (15dPGJ2) downregulate embryonic NO levels. In the presence of NO and superoxide, formation of the potent oxidant peroxynitrite may occur. Therefore, we investigated peroxynitrite-induced damage, ET-1 and 15dPGJ2 concentrations, and the capability of ET-1, 15dPGJ2 and prostaglandin E2 (PGE2) to regulate NO production in embryos from severely diabetic rats (streptozotocin-induced before pregnancy). We found intense nitrotyrosine immunostaining (an index of peroxynitrite-induced damage) in neural folds, neural tube and developing heart of embryos from diabetic rats (P < 0.001 vs controls). We also found reduced ET-1 (P < 0.001) and 15dPGJ2 (P < 0.001) concentrations in embryos from diabetic rats when compared with controls. In addition, the inhibitory effect of ET-1, 15dPGJ2 and PGE2 on NO production found in control embryos was not observed in embryos from severely diabetic rats. In conclusion, both the demonstrated peroxynitrite-induced damage and the altered levels and function of multiple signaling molecules involved in the regulation of NO production provide supportive evidence of nitrosative stress in diabetic embryopathy.

Metalloproteinase 2 activity and modulation in uterus from neonatal streptozotocin-induced diabetic rats during embryo implantation

Matrix metalloproteinases (MMPs) are responsible for the remodelling of the uterine extracellular matrix during embryo implantation. Nitric oxide (NO) production is increased at the time when implantation begins. Abnormal tissue levels of MMPs are present in diabetes; elevated NO levels in tissues and an increased oxidative stress are also found. The present work evaluates the uterine MMP2 activity and levels during embryo implantation, as well as the influence of nitridergic compounds and reactive oxygen species (ROS) on the MMP2 enzymatic activity in a model of neonatal streptozotocin-induced diabetic rat. Metalloproteinase 2 activity and levels are increased in diabetic tissues compared with controls (P < 0.05 and P < 0.002 respectively). The uterine enzymatic activity in diabetic animals decreases in the presence of the NOS inhibitor NG-nitro-L-arginine methyl ester (P < 0.01) and is enhanced (P < 0.005) when a generating ROS system (xanthine/xanthine oxidase) is added to the incubating medium. It was also found that uterine superoxide dismutase activity is higher in diabetic rats than in control rats on the day of implantation (P < 0.001), suggesting a compensatory antioxidant ability. In conclusion, the results show that the uterine MMP2 activity, which is higher in diabetic animals than in control animals, is modulated positively by NO and ROS during embryo implantation in a model of streptozotocin-induced diabetic rats.

Sox17 and beta-catenin cooperate to regulate the transcription of endodermal genes

Recent studies have led to a model of the molecular pathway that specifies the endoderm during vertebrate gastrulation. The HMG box transcription factor Sox17 is a key component of this pathway and is essential for endoderm formation; however, the molecular events controlled by Sox17 are largely unknown. We have identified several direct transcriptional targets of Sox17, including Foxa1 and Foxa2. We show that beta-catenin, a component of Wnt signaling pathway, physically interacts with Sox17 and potentiates its transcriptional activation of target genes. We identify a motif in the C terminus of Sox17, which is conserved in all the SoxF subfamily of Sox proteins, and this motif is required for the ability of Sox17 to both transactivate target genes and bind beta-catenin. Nuclear beta-catenin is present in endoderm cells of the gastrula, and depletion of beta-catenin from embryos results in a repression of Sox17 target genes. These data suggest that in a mechanism analogous to Tcf/Lef interacting with beta-catenin, Sox17 and beta-catenin interact to transcribe endodermal target genes.

Elevated levels of endothelin-1 and prostaglandin E2 and their effect on nitric oxide generation in placental tissue from neonatal streptozotocin-induced diabetic rats

Endothelin-1 (ET-1), nitric oxide (NO) and prostaglandin E(2) (PGE(2)) are regulators of feto-placental hemodynamics. In this study we explore the inter-regulatory pathways that modulate the levels of these vasoactive agents in control and neonatal streptozotocin-induced (n-stz) diabetic rat placenta. ET-1 levels are increased in diabetic placenta when compared to controls (P<0.001), and are strongly reduced by an NO synthase inhibitor (P<0.001). PGE(2) production is increased in diabetic placenta when compared to controls (P<0.01), but these levels are not modulated by ET-1. NO levels, similar in control and in diabetic placenta, are not influenced by PGE(2), but they are negatively modulated by ET-1 in both control (P<0.05) and diabetic (P<0.01) placenta. We conclude that rat placental ET-1 inhibits NO levels but does not modify PGE(2) concentrations. The elevated levels of ET-1 and PGE(2) in diabetic placenta, potent vasoconstrictors of placental vasculature, are probably related to the induction of placental insufficiency and fetal hypoxia in this pathology.

Modulation of nitric oxide concentration and lipid metabolism by 15-deoxy Delta12,14prostaglandin J2 in embryos from control and diabetic rats during early organogenesis

The concentration of 15-deoxy Delta(12,14)PGJ(2) (15dPGJ(2)) and its effects on nitric oxide generation and neutral lipid in embryos from control and neonatal streptozotocin-induced (n-stz) diabetic rats during organogenesis were investigated. 15dPGJ(2) is produced in embryos during organogenesis, and its production is lower in embryos of n-stz diabetic rats than in embryos from control rats. Nitrate and nitrite concentrations were higher in embryos from n-stz diabetic rats and were reduced in the presence of 15dPGJ(2) both in embryos from control and diabetic rats. Thus, decreased 15dPGJ(2) concentrations in embryos from n-stz diabetic rats may be related to the high nitric oxide concentrations found in those embryos. Exogenous 15dPGJ(2) decreased cholesterol and cholesteryl ester concentrations in embryos from control and n-stz diabetic rats, and reduced triacylglycerol concentrations in control embryos. Incorporation of [(14)C]acetate into lipids showed decreased de novo synthesis of cholesteryl ester and triacylglycerides in embryos from n-stz diabetic rats compared with controls. Exogenous 15dPGJ(2) reduced the incorporation of [(14)C]acetate into triacylglycerides, cholesterol and cholesteryl ester in embryos from both control and n-stz diabetic rats. 15dPGJ(2) is present in embryos during organogenesis, and reduces embryonic nitric oxide production and lipid synthesis. The lower 15dPGJ(2) concentration in embryos from n-stz diabetic rats may result in developmental alterations in this diabetic model.

Modulation of nitric oxide concentration and lipid metabolism by 15-deoxy Delta12,14prostaglandin J2 in embryos from control and diabetic rats during early organogenesis

The concentration of 15-deoxy Delta(12,14)PGJ(2) (15dPGJ(2)) and its effects on nitric oxide generation and neutral lipid in embryos from control and neonatal streptozotocin-induced (n-stz) diabetic rats during organogenesis were investigated. 15dPGJ(2) is produced in embryos during organogenesis, and its production is lower in embryos of n-stz diabetic rats than in embryos from control rats. Nitrate and nitrite concentrations were higher in embryos from n-stz diabetic rats and were reduced in the presence of 15dPGJ(2) both in embryos from control and diabetic rats. Thus, decreased 15dPGJ(2) concentrations in embryos from n-stz diabetic rats may be related to the high nitric oxide concentrations found in those embryos. Exogenous 15dPGJ(2) decreased cholesterol and cholesteryl ester concentrations in embryos from control and n-stz diabetic rats, and reduced triacylglycerol concentrations in control embryos. Incorporation of [(14)C]acetate into lipids showed decreased de novo synthesis of cholesteryl ester and triacylglycerides in embryos from n-stz diabetic rats compared with controls. Exogenous 15dPGJ(2) reduced the incorporation of [(14)C]acetate into triacylglycerides, cholesterol and cholesteryl ester in embryos from both control and n-stz diabetic rats. 15dPGJ(2) is present in embryos during organogenesis, and reduces embryonic nitric oxide production and lipid synthesis. The lower 15dPGJ(2) concentration in embryos from n-stz diabetic rats may result in developmental alterations in this diabetic model.

Streptozotocin-pancreatic damage in the rat: modulatory effect of 15-deoxy delta12,14-prostaglandin j(2) on nitridergic and prostanoid pathway

15-deoxy-delta (12,14)prostaglandin J(2) (15d-PGJ(2)) has been identified as a natural ligand of the PPARgamma subtype. PPAR activation in nonadipose tissues seems to inhibit iNOS and COX2 expression. Vasoactive compounds like nitric oxide and prostaglandins are increased in pancreatic tissue from streptozotocin-diabetic rats. We hypothesize that 15d-PGJ(2) may regulate the production of these proinflammatory compounds that lead to beta cell destruction in the diabetic pathology. In this work we evaluated Ca(2+)-dependent (cNOS) and Ca(2+)-independent (iNOS) activity, nitrate/nitrite levels, 15-dPGJ(2) and prostaglandin E(2) (PGE(2)) levels in isolated pancreatic islets, and 15d-PGJ(2) levels in plasma from control and streptozotocin-diabetic rats. Our results show that cNOS is predominant in control, while iNOS isoform is increased in the diabetic islets (P < 0.01). 15d-PGJ(2) 10(-5)M inhibits cNOS and iNOS activity both in control and diabetic islets (P < 0.05). Nitrate/nitrite and PGE(2) levels are higher in diabetic than in control islets (P < 0.05 and P < 0.01, respectively). 15d-PGJ(2) 10(-5)M decreases nitrate/nitrite and PGE(2) levels both in control and in diabetic islets. Bisphenol A diglycidyl ether (BADGE), a recently described PPARgamma antagonist, seems to act as a PPARgamma agonist, diminishing nitrate/nitrite and PGE2 levels in control and diabetic islets. 15d-PGJ(2) production is lower in islets from diabetic animals compared to control (P < 0.05). Our observations suggest that 15d-PGJ(2) is able to diminish the production of vasoactive proinflammatory agents in pancreatic islets. The diminished 15d-PGJ(2) levels in the diabetic islets are probably related to the diminished capacity to limit the inflammatory response due to experimental diabetes in the rat.

Membrane-type matrix metalloproteinase-9 activity in placental tissue from patients with pre-existing and gestational diabetes mellitus

The activity of matrix metalloproteinase (MMP)-9 was evaluated in placental tissue from healthy subjects (controls) and from patients with gestational and pre-existing diabetes mellitus (GDM and PDM, respectively). Compared with controls, MMP-9 activity was greater in placental tissue from patients with PDM and lower in placental tissue from patients with GDM. The modulatory role of nitric oxide (NO) and reactive oxygen species (ROS) on MMP-9 activity in placental tissue was evaluated. In healthy placenta, NO synthase inhibitors diminished MMP-9 activity, whereas NO donors enhanced it. The addition of xanthine/xanthine oxidase or hydrogen peroxide to placental incubates enhanced MMP-9 activity, while the addition of superoxide dismutase (SOD) diminished it. In placental tissue from patients with PDM, MMP-9 activity was stimulated by NO and by ROS. In placental tissue from patients with PDM, concentrations of nitrates/nitrites and thiobarbituric acid-reactive substances (TBARS) were enhanced, whereas SOD activity was decreased, suggesting that elevated concentrations of NO and ROS may be related to the enhanced MMP-9 concentrations found in these tissues. In placenta from GDM patients, in which a diminished concentration of MMP-9 were detected, nitrate/nitrite concentrations were increased, but placental MMP-9 activity did not change in the presence of either NO donors or inhibitors. The activity of MMP-9 in placental tissue from patients with GDM was stimulated by ROS donor systems and was inhibited by the addition of SOD; however, TBARS and SOD concentrations were unchanged in these tissues compared with controls. These findings demonstrate that placental MMP-9 activity is modulated by NO and ROS and that, in diabetic pathology, NO and ROS may determine changes in MMP-9 activity, which are probably involved in the structural and functional abnormalities of diabetic placental tissue.

Diminished PGE2 content, enhanced PGE2 release and defects in 3H-PGE2 transport in embryos from overtly diabetic rats

Diminished PGE2 levels in diabetic embryos are related to the development of malformations, and thus the aim of the present study was to determine whether PGE2 levels are modified in rat embryos cultured in diabetic serum during organogenesis, and if PGE2 content and release, and 3H-PGE2 uptake and release, are altered in incubated diabetic embryos. Rats were made diabetic by steptozotocin (60 mg kg(-1)) before mating. Control rat embryos cultured for 24 h (explantation Day 9) in the presence of diabetic serum showed diminished PGE2 levels. When Day 10 diabetic embryos were incubated, embryo PGE2 levels were lower, but the PGE2 released to the incubation media was much higher than in controls. Uptake of 3H-PGE2 by diabetic embryos was initially enhanced (5-10 min), then reached similar levels to controls (20-100 min). Release of 3H-PGE2 previously incorporated during a 60-min incubation was greater in diabetic embryos than in controls. These results show diminished PGE2 content in both diabetic and normal embryos cultured in the presence of diabetic serum, but suggest that diabetic embryos have the capability to produce and release high levels of PGE2. The enhanced release of PGE2 is probably the result of transport abnormalities, and leads to the elevated PGE2 concentrations found in the incubating medium and to the diminished intraembryonic PGE2 levels that alter embryonic development.

Involvement of inducible isoforms of COX and NOS in streptozotocin-pancreatic damage in the rat: interactions between nitridergic and prostanoid pathway

Streptozotocin-induced pancreatic damage involves nitric oxide (NO) and prostaglandins (PGs) overproduction. In this work we aim to evaluate a putative relationship between the elevated NO levels and the altered prostanoid production in pancreatic tissue from streptozotocin-diabetic rats. Total NOS activity and nitrate/nitrite pancreatic levels in tissues from diabetic rats are decreased when the cyclooxygenase (COX) inhibitor indomethacin (INDO) is added to the incubating medium, while the addition of PGE(2)increases nitrate/nitrite production and NOS levels. INDO and PGE(2)selectively affect Ca(2+)-dependent NOS (iNOS) activity in diabetic tissues, and they have not been able to modify nitrate/nitrite levels, iNOS or Ca(2+)-dependent (cNOS) in control tissues. When the NOS inhibitor L-NMMA was present in the incubating medium, control pancreatic [(14)C]-Arachidonic Acid ([(14)C]-AA) conversion to 6-keto PGF(1 alpha)and to TXB(2)was lower, and PGF(2 alpha), PGE(2)and TXB(2)production from diabetic tissues diminished. The NO donors, spermine nonoate (SN) and SIN-1, enhanced TXB(2)levels in control tissues, while PGF(2 alpha), PGE(2)and TXB(2)levels from diabetic tissues were increased. PGE(2)production from control and diabetic tissues was assessed in the presence of the NO donor SN plus INDO or NS398, a specific PG synthase 2 inhibitor. When SN combined with INDO or NS398 was added, the increment of PGE(2)production was abolished by both inhibitors in equal amounts, indicating that the activating effect of nitric oxide is exerted on the inducible isoform of cyclooxygenase. In the diabetic rat, prostaglandins and NO seem to stimulate the generation of each other, suggesting a lack of regulatory mechanisms that control the levels of vasoactive substances in acute phase of beta-cell destruction.

Modulation of PGE2 generation in the diabetic embryo: effect of nitric oxide and superoxide dismutase

In this work we assessed NO levels in the control and diabetic embryo during early organogenesis, and the ability of NO and SOD to modify embryonic PGE2 levels. Rats were made diabetic by steptozotocin (60 mg/kg) before mating. Diabetic embryos (day 10 of gestation) show increased nitrate/nitrite levels and enhanced NOS activity. The diabetic embryos release to the incubation medium increased amounts of PGE2 and have diminished PGE2 content. In the control embryo NO modulates PGE2 levels, but this modulatory pathway is not observed in the diabetic embryos. The diminished PGE2 content and the enhanced PGE2 release is prevented by SOD additions, both in the diabetic embryos and in control embryos cultured in the presence of diabetic serum (24 h culture, explantation day 9). The present results show that SOD additions prevent the abnormalities in the accumulation, production and release of PGE2 in diabetic embryos, probably related to the decrease in malformations.

Pancreatic nitric oxide and oxygen free radicals in the early stages of streptozotocin-induced diabetes mellitus in the rat

The objective of the present study was to explore the regulatory mechanisms of free radicals during streptozotocin (STZ)-induced pancreatic damage, which may involve nitric oxide (NO) production as a modulator of cellular oxidative stress. Removal of oxygen species by incubating pancreatic tissues in the presence of polyethylene glycol-conjugated superoxide dismutase (PEG-SOD) (1 U/ml) produced a decrease in nitrite levels (42%) and NO synthase (NOS) activity (50%) in diabetic but not in control samples. When NO production was blocked by N(G)-monomethyl-L-arginine (L-NMMA) (600 microM), SOD activity increased (15.21 +/- 1.23 vs 24.40 +/- 2.01 U/mg dry weight). The increase was abolished when the NO donor, spermine nonoate, was added to the incubating medium (13.2 +/- 1.32). Lipid peroxidation was lower in diabetic tissues when PEG-SOD was added (0.40 +/- 0.02 vs 0.20 +/- 0.03 nmol/mg protein), and when L-NMMA blocked NOS activity in the incubating medium (0.28 +/- 0.05); spermine nonoate (100 microM) abolished the decrease in lipoperoxide level (0.70 +/- 0.02). We conclude that removal of oxygen species produces a decrease in pancreatic NO and NOS levels in STZ-treated rats. Moreover, inhibition of NOS activity produces an increase in SOD activity and a decrease in lipoperoxidation in diabetic pancreatic tissues. Oxidative stress and NO pathway are related and seem to modulate each other in acute STZ-induced diabetic pancreas in the rat.

Evolution of streptozotocin-pancreatic damage in the rat: modulatory effect of endothelins on the nitridergic and prostanoid pathway

Many lines of evidence indicate that an increased pancreatic production of nitric oxide (NO) and prostaglandins (PGs) is found in the pancreas of streptozotocin-diabetic rats and that endothelins (ETs) are closely related to the nitridergic and prostanoid pathway in several tissues. In the present study the relationship between NO, ETs, and PGs has been explored in isolated pancreatic tissue from streptozotocin-diabetic rats. Pancreatic ET levels are higher in pancreatic tissues from diabetic (D) rats compared to control (C) animals. The addition of nitric oxide synthase (NOS) inhibitors (1 mM N(G)-nitro-l-arginine methyl ester, 600 microM N(G)-monomethyl-l-arginine) in the incubating medium reduces and NO donors (SIN-1, 300 microM spermine suppress, NONOate 100 microM) increases ET levels in pancreatic slices from C and D animals. PGE(2) (10(-7) M) increases and indomethacin (10(-6) M) decreases ET pancreatic production only in D but not in C tissues when added into the incubating bath. When tissues are incubated in the presence of endothelin 1 (ET-1) (10(-7) M), NOS activity is higher in C pancreas, while the ET-receptor antagonist bosentan (B) decreases NOS levels in D but not in C tissues. When pancreatic arachidonic acid (AA) conversion to prostaglandins was explored, ET-1 increased PGF(2alpha), PGE(2), and TXB(2) levels in C but not in D tissues. B abolishes TXB(2) increment due to the diabetic state, but failed in modulating AA conversion to 6-keto PGF(1alpha), PGF2(alpha) and PGE(2) in D pancreas. Our results show an alteration in AA metabolism, ET production, and NO increment associated with pancreatic damage due to streptozotocin.

Increased prostaglandin E generation and enhanced nitric oxide synthase activity in the non-insulin-dependent diabetic embryo during organogenesis

Embryonic development, prostaglandin E (PGE) generation and nitric oxide synthase (NOS) activity during organogenesis were evaluated in an experimental rat model of non-insulin-dependent diabetes (NIDD) generated by neonatal administration of streptozotocin. Gross malformations were detected in 5% of NIDD embryos and these embryos were all non-viable; in the other 95%, growth was retarded but no congenital abnormalities were found. Control embryos were all alive and not malformed. The NIDD 11-day embryos secreted more PGE into the incubation medium than did controls. The NO donor SIN-1 increased PGE production in both control and NIDD embryos. A NOS inhibitor (L-NMMA) reduced PGE generation in both experimental groups, suggesting a modulatory role of NO on embryonic PGE production. Activity of NOS was higher in NIDD 11-day embryos than in controls. Treatment in vivo of control and NIDD rats (Days 7-11 of gestation) with a NOS inhibitor (L-NAME; 5 mg kg(-1) i.p.) reduced embryonic PGE production and induced a higher resorption rate and an increase in neural-tube defects. The results suggest that NO modulates PGE generation in the organogenetic embryo. In the NIDD model, overproduction of NO is observed, this NO probably enhancing embryonic PGE production. The relationship between PGE generation and the appearance of congenital abnormalities is discussed.

Nitric oxide modulates placental prostanoid production from late pregnant non-insulin-dependent diabetic rat

Severe reproductive dysfunction has been described in non-insulin-dependent diabetes mellitus (NIDDM), correlated with high glucose levels in the plasma. We have characterized an abnormal prostanoid profile in tissues from NIDDM rats, and a tight correlation between nitric oxide (NO) levels and prostaglandin production. Likewise, we have determined that parturition is delayed in NIDDM rats compared to control animals. In order to characterize the events which precede delayed parturition in NIDDM rats, we evaluate (a) the arachidonic acid (AA) conversion in placental tissue obtained from control (day 21 and 22) and NIDDM (day 21, 22 and 23) late pregnant rats into prostaglandin E2 (PGE2) and F2alpha (PGF2alpha), thromboxane B2 (TXB2) and 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha), and (b) NO synthase (NOS) activity in control and NIDDM late pregnant animals. Placental arachidonate conversion from control rats into different prostanoids, namely PGE2, PGF2alpha, and TXB2, is higher in day 22 than in day 21, and radioconversion from diabetic rats into PGE2, PGF22, TXB2 and 6-keto-PGF1alpha on day 23 is higher than in day 21 and 22. 6-keto-PGF1alpha is lower and TXB2 is higher in diabetic tissues than in control. Placental AA conversion of control diabetic tissues on the day of delivery is decreased by N(G) monomethyl-L-arginine (LNMMA) (600 mM), a well known NOS inhibitor, while prostanoid production remains unaltered on previous days. NOS activity is higher in control on day 22 when compared to day 21, and in diabetic on day 23 when compared to day 22 of pregnancy. We conclude that elevated NO placental levels are observed in control (day 22) and NIDDM (day 23) rats, and may increase placental prostaglandin production on the day of delivery.